################homework-2

###############create random list
import random
lst1 = ([random.randint(1,20) for i in range(20)])
#print(lst1)

############# cout random to list
lst2 = list()
for i in range(20):
    lst2.append((lst1[i],lst1.count(lst1[i]))) # 这里的count效率会有影响

############# list-->set-->list

lst3 = list(sorted(set(lst2),reverse=True))
print(lst3)
for j in range(3):
    print(lst3[j])

# 有许多没必要的数据转换
